Generally, as the industry is getting sophisticated, there is an increasing need to control particles such as dust and the like in production sites as well as in office environments, and thus a clean room was introduced to keep the production site clean at all times and thus to prevent adverse effects on the product by the particles.
Such a clean room refers to a space where contamination control is performed by controlling the concentration of the particles floating in the air within a indicated cleanliness level limit, wherein the space is also controlled and managed for environmental conditions such as temperature, humidity, room pressure, illuminance, noise, and vibration, if necessary. These clean rooms are currently being installed and operated in various industries including semiconductors, LCD displays, aviation, pharmaceuticals, hospitals, food and the like.
Especially, in the high-tech industry including a highly precise process at nano-level such as a semiconductor manufacturing process, a LCD display manufacturing process and the like, since minute environmental conditions at the site where the product is manufactured can also have a great influence on the quality of the product, the cleanliness which is required in the clean room is getting stronger. For example, in the semiconductor manufacturing process, it is pointed out that pattern defects caused by deposition of particles oscillated from an automation device or the like on the surface of the wafer are the main causes of the yield reduction of the product.
As such, if the particles are present at the site where the product is manufactured, the particles may be transferred to the product during the manufacturing process and thus may cause fatal product defect. These particles are accumulated on ceilings, walls, floors, production and measurement equipment, various equipment and the like of the site where the product is manufactured, and are attached to the surface of the worker's clothing, and when causing the movement of airflow due to the movement of robots, workers and products, and the spatial imbalance of temperature, the surface particles accumulated on the surface of workers, objects, or their adjacent portions will be transferred to contaminate the product, thereby causing product defect.
In general, a method for collecting the suspended particles in the air with a filter paper is used, but since these particles in the clean room are usually very small in diameter and may not be visible to the naked eye, a separate particle detector for measuring contaminants in the clean room is used, and then, by using this particle detector, the particle distribution state in a specific chamber of a facility is being measured in real time.
As a specific prior art, Korean Patent Registration No. 10-0567789 (published on Apr. 5, 2006) discloses a particle measuring device consisting of a particle charging mean for charging particles; an internal guide duct through which clean air is introduced; an electrode which is installed longitudinally in the internal guide duct; a plurality of particle separators which are located outside the internal guide duct, which are longer than the length of the internal guide duct, and into which particles charged by a particle charging mean located between with the internal guide duct are entered, and which are provided with an external guide duct having a particle collection portion at the downstream; a power supply mean for providing different power sources such that a voltage difference is occurred at each electrode of a plurality of particle separators; and a plurality of particle counting means for measuring the number of particles collected by the particle separators.
In addition, as another prior art, Korean Patent Registration No. 10-1264075 (published on May 13, 2013) discloses an optical particle measuring device characterized in that the device comprises a suction portion through which air is sucked into a measurement space; a measurement chamber having an outlet through which air passed through the interior of the measurement space is discharged; a plurality of light source portions adapted to illuminate the interior of the measurement space of the measurement chamber with light having different wavelengths; a plurality of photo-detection portions for detecting light which is irradiated from a plurality of light sources respectively and is scattered by the particles contained in the air passing through the interior of the measurement space, and thus generating an electrical signal corresponding to the amount of light therefrom; a light removal portion for removing light which is irradiated from a plurality of light sources respectively and is not scattered by the particles; a plurality of computation portions for calculating the particle size distribution and the number of particles by size from the magnitude and frequency of the electrical signals detected respectively by a plurality of photo-detection portions; and a plurality of mirrors which are disposed one by one on the opposite side of each of a plurality of photo-detection portions and can reflect the scattered light toward the corresponding photo-detection portions, wherein a plurality of mirrors are arranged such that the lights reflected by a plurality of mirrors do not overlap with each other and a plurality of light source portions simultaneously irradiate light having different wavelengths into the interior of the measurement space.
However, since the above-described prior arts require to separately purchase an expensive particle measuring device for particle measurement, there is a problem not only that a lot of cost is required, but also that the operation of the equipment is complicated, a long time is required for inspection, and a large space is required because of the large size of the equipment.
Also, particle measuring devices according to the above-described prior art can measure the number, size, or distribution of the whole particles in the clean room, but there is a problem in that it is difficult to identify the sampled specimen and it is impossible to judge from which object the collected particles are generated, and to judge the place where the object entered along with a large amount of particles is located, and thus it is difficult to control contamination by particles in the clean room.
In addition, although there is a method of cleaning the surface of the object to be measured with clean water and then counting the particles with a counter for counting particles in the liquid, there is a problem in that it is difficult to detect particles which are dissolved in water and liquefied because the particles are washed with water and detected in water.